If we talk about old public housing in Singapore, that would be Toa Payoh. Toa Payoh (大巴窑), located in the Central Region, is one of the oldest districts in Singapore. It had the first few satellite public housing estates of Singapore built there. The name itself is Hokkien and it means "big swamp" as there was a swampy area that preceded the later development of the market garden of Chinese people there.
If you happen to visit Toa Payoh now, it has changed to a well-developed area with high rise buildings (Toa Payoh HDB Hub), public housing estates of 40 storeys, shopping mall, and many more. Despite all these developments, there are a few older public housing estates still standing in Toa Payoh and most of the elderly people live there. The letter boxes (what you see in the photos) used there are still the older ones which you can hardly see around in Singapore anymore. In addition, there are a number of Chinese temples in Toa Payoh and one of them, Shaung Ling Shi is one of the famous temples in Singapore. As for the food, yes it is a food heaven and is also where you can find lots of delicious local delights.
If you are into old places do consider a visit to Toa Payoh.